Change of coordinates X,Y-> θ, ρ

22

tan

YX

X

YA

Entirely direct or sequential

mechanisms are not able to explain

experimental data!

1 INFN Sezione di Catania, Catania (Italy), 2 Università di Catania Dip. di Fisica e Astronomia, Catania (Italy), 3 Instituto de Fìsica Universidad Nacional Autònoma de México, México City (Mexico), 4 Università di Messina

Dip. di Scienze Matematiche ed Informatiche, Scienze Fisiche e Scienze della Terra, e INFN Sezione di Catania, Messina (Italy), 5 GANIL CEA-IN2P-CNRS, Caen (France), 6 INFN, Laboratori Nazionali del Sud , Catania (Italy), 7 Departamento de Fìsica Aplicada Universitad de Huelva, Huelva (Spain), 8 INFN Sezione di Napoli, Napoli (Italy), 9 IPN Orsay, Orsay (France), 10 Università Kore, Enna (Italy), 11Università di Napoli Federico II Dipartimento di Fisica, Napoli (Italy), 12 Slovak Academy of Sciences, Bratislava (Slovakia), 13CNR- IPCF, Messina (Italy), †Decease

Two-particle correlations allow to explore dynamics of heavy ion collisions and also to

access some structure properties of produced systems.

These techniques are also extended to multi particle correlations to explore the competition between direct and

sequential decay of observed resonances.

A study of two and multi particle correlations in 12C+24Mg reaction at E=35 AMeV has been performed at Laboratori Nazionali del Sud of Catania by using the forward part of

CHIMERA 4π multi detector.

7.74 MeV (Hoyle state)

9.83 MeV

3α Correlation Function

)(

)()(1

exuncorr

excoinex

EY

EYER

Coincidence yield spectrum

constructed using three alpha particles

detected in coincidence in the

same event

Uncorrelated yield spectrum

constructed with a randomization of

experimental spectra

Monte-Carlo Simulations filtered through the geometry and detector response of CHIMERA.

F. G

renie

r et a

l., N

ucl. P

hys. A

811

, 2

33

(2

00

8).

Po

ch

od

za

lla e

t a

l., P

hys.R

ev.

C.3

5.1

69

5.(

198

7)

In particular three α correlations have been explored with the aim of studying the competition between different decay

processes of resonances produced in 12C

The α particles resulting from the decay of 12C quasi-projectiles, are selected by requiring the parallel velocity, reconstructed from their center of mass, to

be larger than 80% of beam velocity.

In order to study decay mechanisms of the observed resonances, possibly disentangling sequential decays from direct three-body ones, a procedure based on construction of Dalitz plots has been

followed.

Hoyle State

)/(,,,, kjikjikji EEEE

kji

kj

y

x

2

)(3

Symmetric Dalitz plots

Particles energies in 12C* frame normalized to the total energy of 3α decay

Kirsebom et al., Physical Review Letters 108 202501, (2012)

Experimental results Experimental plot exhibits a more uniform

distribution that does not allow us to exclude any of the two decay mechanisms…

For better evaluation εi distribution has been

analyzed!

εi DISTRIBUTION

State at E*=9.64 MeV

3/)2(

3/)(3

213

21

CMCMCM

CMCM

EEEy

EEx

Dalitz parameters

SEQUENTIAL DIRECT

Monte-Carlo Simulations filtered through the geometry and detector response of CHIMERA.

Experimental results 12C+24Mg

12C+24Mg

FIT OF εi DISTRIBUTION

εi distribution gives us information about decay

processes

t-α CORRELATION FUNCTION

Information on excited states of 7Li!

3α CORRELATION FUNCTION

M. Itoh et al., Phys. Rev. Lett. 113 102501, (2014).

The agreement between simulated and

experimental data improves when increasing the percentage of direct

decay component

FIT OF θ DISTRIBUTION

The best fit is obtained mixing 60% of sequential

processes with 40% of the direct

ones.

In order to extract a quantitative

estimation of these relative contributions

CONCLUSIONS A strong contribution of direct decay mechanism is present in both the analyzed

resonances of 12C.

These observations could be related to In- medium effects on nuclear structure properties.

Analysis at different energies and reaction systems to evaluate possible medium effect!!

Study of two and multi particle correlations in 12C+24Mg reaction at E=35 AMeV

12C+24Mg E=53 and 95 AMeV

with INDRA

SEQUENTIAL DIRECT

L. Quattrocchi1,2, L. Acosta2,3, L. Auditore4, G. Cardella1, A. Chbihi5, E. De Filippo1 , S. De Luca4, D. Dell’ Aquila8,11, L. Francalanza8, B. Gnoffo1,2, G. Lanzalone6,10, I. Lombardo8,11, I. Martel7, N. S. Martorana2,6, S. Norella4, A. Pagano1 , E.V. Pagano2,6, M. Papa1, S. Pirrone1, G. Politi1,2, F. Porto2,6, F. Rizzo2,6, E. Rosato8,11†, P. Russotto1, A. Trifirò4,

M. Trimarchi4, G. Verde1,9, M. Veselsky12, M. Vigilante8,11